/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License, version 2.0 (the
 * "License"); you may not use this file except in compliance with the License. You may obtain a
 * copy of the License at:
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License
 * is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
 * or implied. See the License for the specific language governing permissions and limitations under
 * the License.
 */
package io.netty.example.http2.helloworld.client;

import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInboundHandlerAdapter;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.socket.SocketChannel;
import io.netty.handler.codec.http.DefaultFullHttpRequest;
import io.netty.handler.codec.http.HttpClientCodec;
import io.netty.handler.codec.http.HttpClientUpgradeHandler;
import io.netty.handler.codec.http.HttpMethod;
import io.netty.handler.codec.http.HttpVersion;
import io.netty.handler.codec.http2.DefaultHttp2Connection;
import io.netty.handler.codec.http2.DelegatingDecompressorFrameListener;
import io.netty.handler.codec.http2.Http2ClientUpgradeCodec;
import io.netty.handler.codec.http2.Http2Connection;
import io.netty.handler.codec.http2.Http2FrameLogger;
import io.netty.handler.codec.http2.HttpToHttp2ConnectionHandler;
import io.netty.handler.codec.http2.HttpToHttp2ConnectionHandlerBuilder;
import io.netty.handler.codec.http2.InboundHttp2ToHttpAdapterBuilder;
import io.netty.handler.ssl.ApplicationProtocolNames;
import io.netty.handler.ssl.ApplicationProtocolNegotiationHandler;
import io.netty.handler.ssl.SslContext;

import static io.netty.handler.logging.LogLevel.INFO;

/**
 * Configures the client pipeline to support HTTP/2 frames.
 */
public class Http2ClientInitializer extends ChannelInitializer<SocketChannel>
{
    private static final Http2FrameLogger logger = new Http2FrameLogger(INFO,
            Http2ClientInitializer.class);

    private final SslContext sslCtx;

    private final int maxContentLength;

    private HttpToHttp2ConnectionHandler connectionHandler;

    private HttpResponseHandler responseHandler;

    private Http2SettingsHandler settingsHandler;

    public Http2ClientInitializer(SslContext sslCtx, int maxContentLength)
    {
        this.sslCtx = sslCtx;
        this.maxContentLength = maxContentLength;
    }

    @Override
    public void initChannel(SocketChannel ch) throws Exception
    {
        final Http2Connection connection = new DefaultHttp2Connection(false);
        connectionHandler = new HttpToHttp2ConnectionHandlerBuilder()
                .frameListener(
                        new DelegatingDecompressorFrameListener(connection,
                                new InboundHttp2ToHttpAdapterBuilder(connection)
                                        .maxContentLength(maxContentLength)
                                        .propagateSettings(true).build()))
                .frameLogger(logger).connection(connection).build();
        responseHandler = new HttpResponseHandler();
        settingsHandler = new Http2SettingsHandler(ch.newPromise());
        if (sslCtx != null)
        {
            configureSsl(ch);
        }
        else
        {
            configureClearText(ch);
        }
    }

    public HttpResponseHandler responseHandler()
    {
        return responseHandler;
    }

    public Http2SettingsHandler settingsHandler()
    {
        return settingsHandler;
    }

    protected void configureEndOfPipeline(ChannelPipeline pipeline)
    {
        pipeline.addLast(settingsHandler, responseHandler);
    }

    /**
     * Configure the pipeline for TLS NPN negotiation to HTTP/2.
     */
    private void configureSsl(SocketChannel ch)
    {
        ChannelPipeline pipeline = ch.pipeline();
        pipeline.addLast(sslCtx.newHandler(ch.alloc()));
        // We must wait for the handshake to finish and the protocol to be
        // negotiated before configuring
        // the HTTP/2 components of the pipeline.
        pipeline.addLast(new ApplicationProtocolNegotiationHandler("")
        {
            @Override
            protected void configurePipeline(ChannelHandlerContext ctx,
                    String protocol)
            {
                if (ApplicationProtocolNames.HTTP_2.equals(protocol))
                {
                    ChannelPipeline p = ctx.pipeline();
                    p.addLast(connectionHandler);
                    configureEndOfPipeline(p);
                    return;
                }
                ctx.close();
                throw new IllegalStateException(
                        "unknown protocol: " + protocol);
            }
        });
    }

    /**
     * Configure the pipeline for a cleartext upgrade from HTTP to HTTP/2.
     */
    private void configureClearText(SocketChannel ch)
    {
        HttpClientCodec sourceCodec = new HttpClientCodec();
        Http2ClientUpgradeCodec upgradeCodec = new Http2ClientUpgradeCodec(
                connectionHandler);
        HttpClientUpgradeHandler upgradeHandler = new HttpClientUpgradeHandler(
                sourceCodec, upgradeCodec, 65536);

        ch.pipeline().addLast(sourceCodec, upgradeHandler,
                new UpgradeRequestHandler(), new UserEventLogger());
    }

    /**
     * A handler that triggers the cleartext upgrade to HTTP/2 by sending an
     * initial HTTP request.
     */
    private final class UpgradeRequestHandler
            extends ChannelInboundHandlerAdapter
    {
        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception
        {
            DefaultFullHttpRequest upgradeRequest = new DefaultFullHttpRequest(
                    HttpVersion.HTTP_1_1, HttpMethod.GET, "/");
            ctx.writeAndFlush(upgradeRequest);

            ctx.fireChannelActive();

            // Done with this handler, remove it from the pipeline.
            ctx.pipeline().remove(this);

            configureEndOfPipeline(ctx.pipeline());
        }
    }

    /**
     * Class that logs any User Events triggered on this channel.
     */
    private static class UserEventLogger extends ChannelInboundHandlerAdapter
    {
        @Override
        public void userEventTriggered(ChannelHandlerContext ctx, Object evt)
                throws Exception
        {
            System.out.println("User Event Triggered: " + evt);
            ctx.fireUserEventTriggered(evt);
        }
    }
}
